1. Field of the Invention
The present invention relates to power converters, or more particularly, to a system and method of dynamically controlling a power converter's output voltage slew rate, or rate of rise and/or decay.
2. Description of Related Art
Electronic circuits typically include a plurality of electronic loads, in which each load is required to be driven (or powered) in a particular sequence and by a voltage having a particular slew rate. The traditional method of accomplishing this is through the use of a plurality of power converters (e.g., voltage regulators, DC/DC converters, etc.) an external controller, and external circuitry (e.g., external transistor switches, etc.). Specifically, the power converters are adapted to convert a single input voltage into a plurality of output voltages, where each output voltage corresponds to a particular load. Each voltage is then provided to a corresponding load via an external transistor switch. This enables the external controller, via its connection to each transistor switch, to control when and how each output is provided. In other words, by activating and modulating the transistor switches, the controller manages the order in which the voltages are provided and their slew rates.
While most power converters have an internal mechanism (e.g., an internal error-amplifier circuit) for marginally adjusting the power converter's output voltage, these mechanisms are traditionally hardwired and are unrelated to slew rate. Specifically, internal error-amplifier circuits typically include a plurality of input leads, including a positive sense lead (e.g., to receive+Vout), a negative sense lead (e.g., to receive−Vout), and a trim lead (e.g., to receive Vref). The trim lead is typically hardwired (e.g., using a resistor, etc.) to either the positive or negative sense lead, depending on whether the output voltage is to be maintained below or above a particular voltage level. The voltage at the trim lead (i.e., the reference voltage) is then used by the error-amplifier circuit to adjust (or trim) the output voltage. Thus, the traditional method of dynamically controlling a power converter's output voltage slew rate is through the use of an external transistor switch, as previously discussed.
The drawbacks of this method, however, is that it adds complexity, expense and size to the power system by requiring a plurality of external components (e.g., external transistor switches, etc.) and a plurality of traces connecting these components to the external controller. Thus, it would be advantageous to have a system and method of dynamically controlling output voltage slew rate that overcomes at least one of these drawbacks.